Bitcoin Core Refference Wallet HD?

[McMurdo]

Is the bitcoin core reference wallet HD?

or if I run:

$ bitcoin-cli backupwallet

is it only saving my private keys that I have used thus far, and is not backing up my private future keys?

Thank you.

[GSpgh]

Yes, Bitcoin Core wallet is HD since 0.14 (?) but you still might want to make regular backups since the wallet can have private keys outside of the derivation path (e.g. imported via importprivkey).

[HCP]

$ bitcoin-cli backupwallet

The backupwallet command simply creates a copy of your wallet.dat file at the location provided in the command:

backupwallet "destination"

Safely copies current wallet file to destination, which can be a directory or a path with filename.

Arguments:
1. destination    (string, required) The destination directory or file

It is the same as using "File -> Backup wallet..." option in the GUI... or simply manually copying the wallet.dat file (after bitcoind/Bitcoin Core is shut down properly)

[pooya87]

is it only saving my private keys that I have used thus far, and is not backing up my private future keys?

if you want to keep a digital backup of your wallet and keys then backing up the wallet.dat file once (as was explained above) is enough as long as your wallet shows HD in GUI (which is the default setting of newer versions of core).
but if you want to keep a physical backup (eg. on paper) then the only "easy" way is to write down the keys individually. and i believe dumpwallet command and storing the seed (entropy, don't confuse with mnemonic) it shows could be used to re-generate the wallet but it is not the "easy" way.